Summary: Angiogenesis, defined as formation of new blood vessels, is a physiological process necessary for embryonic development and wound repair. Angiogenesis is also an important component of various pathologic events such as tissue ischemia, cancer, diabetic retinopathy, and chronic inflammatory states including atherosclerosis. Among the key events leading to angiogenesis is generation of reactive oxygen species (ROS) such as superoxide anions and hydrogen peroxide which play a key role in physiological and pathophysiological states. LOX-1, a lectin-like ox-LDL receptor, is responsible for binding and uptake of ox-LDL in endothelial cells. It has been well documented that the activation of LOX-1 itself can stimulate the formation of ROS and initiate a cascade of redox-sensitive signaling events. We postulate that oxidized LDL (ox-LDL) at low concentrations activates LOX-1 in endothelial cells, induces low levels of ROS release and initiates the angiogenic response. Our specific aims in this proposal are: Aim # 1: To study the effect of oxidized LDL (ox-LDL) on angiogenesis- These studies will be done in human coronary artery endothelial cells, in an aortic ring model of angiogenesis, as well as in wild-type and LOX-1 knock out (KO) mice. Aim # 2: To define the mechanisms of ox-LDL-induced angiogenic response- These studies will involve a number of specific inhibitors, LOX-1 antibody, siRNA against LOX-1, and upregulation of LOX-1, and will involve state-of-art molecular biology approaches. Further, to define the mechanism of the effects of ox-LDL, microarray technology will be utilized to identify genes that are up-regulated and down-regulated during angiogenesis. The strengths of the proposal are: 1. The PI has strong background on angiogenesis and LOX-1 research. 2. The PI has LOX-1 KO mice in his possession. 3. Availability of well trained molecular biologist well-versed in most aspects of the research. 4. One of the PI's team members has extensive experience in microarray technology. Significance: Understanding of the basis of formation of neovasculature may provide novel information on the basis of atherogenesis, especially in the development of unstable lesions. Information gained from this study may also have relevance in the development of cancers which are dependent of neovasculature for their growth. PUBLIC HEALTH RELEVANCE: Narrative Hardening of the arteries (also known as atherosclerosis) is the cause of heart attacks. As the area covered with atherosclerosis grows, there is formation of small new blood vessels;a process called "angiogenesis". Angiogenesis is caused in part by oxygen-derived molecules called reactive oxygen species (ROS). Our work has shown that ROS stimulate a receptor for oxidized cholesterol called LOX- 1. The proposed experiments are designed to test the concept that oxidized cholesterol at low concentration activates LOX-1, induces low levels of ROS release and initiates angiogenesis. In contrast, high concentration of ROS causes much LOX-1 expression and cell injury. To confirm the role of LOX-1 in angiogenesis, we will use specialized mice that lack the LOX-1. In the second set of experiments, we will study the underlying mechanisms of angiogenesis by examining changes in genes. Information from this study may be important in understanding the development of atherosclerosis and certain cancers that are dependent of angiogenesis.